1. Field of the Invention
This invention relates to a process for the preparation of ortho-(alkyl- or arylthio)phenols by using certain amorphous and crystalline aluminosilicates and/or other strong acids as catalysts for the reaction of phenols with dialkyl or diaryl disulfides and/or certain (alkyl- or arylthio)phenols as (alkyl or aryl)thiolating agents, and for the isomerization of (alkyl- or arylthio)phenols.
2. Description of Related Art
Ortho-(alkylthio)phenols are used to prepare agricultural chemicals such as herbicides. U.S. Pat. No. 4,324,920, issued on Apr. 13, 1982 and the article by P. F. Ranken et al. entitled "Alkylthiolation of Phenols", Synthesis, February 1984, pp. 117-9 disclose a process for the preparation of ortho-(alkylthio)phenols along with lesser amounts of para-(alkylthio)phenols by contacting phenols with dialkyl disulfides in the presence of aluminum phenoxide catalysts. U.S. Pat. No. 2,923,743, issued on Feb. 2, 1960, discloses a process for the preparation of ortho-(alkylthio)phenols by contacting phenols with dialkyl disulfides in the presence of at least equimolar quantities of condensation agents, such as aluminum chloride, aluminum bromide, ferric chloride, zince chloride, tin tetrachloride, antimony pentachloride, or boron fluoride. Examples 4 and 5 of the U.S. Pat. No. 2,923,743 show that lesser amounts of ortho-(alkylthio)phenols relative to the para isomers are produced when the condensation agent is a bleaching earth or activated bleaching earth such as Tonsil.RTM..
It is disclosed in U.S. Pat. No. 3,134,818 issued May 26, 1964, Belgian Pat. No. 626,874, Canadian Pat. No. 714,094, and Journal of Organic Chemistry, 28, 2807 (1963) that the preparation of para-(alkylthio)phenols along with lesser amounts of ortho-(alkylthio)phenols can be effected by reaction of phenols with dialkyl disulfides in the presence of acid catalysts such as phosphoric acid, polyphosphoric acid, concentrated sulfuric acid, alkanesulfonic acid, arenesulfonic acid, and specific cationic ion-exchange resins. U.S. Pat. No. 4,547,593 issued Oct. 15, 1985 discloses the preparation of (hydrocarbylthio)phenols by heating one or more mono- or poly(hydrocarbylthio)phenols in the presence of aluminum phenoxide catalysts to redistribute the starting materials.